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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/UsersManual.rst | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/docs/UsersManual.rst b/docs/UsersManual.rst index f004f20909..88cb72c9b6 100644 --- a/docs/UsersManual.rst +++ b/docs/UsersManual.rst @@ -1745,7 +1745,8 @@ controlled by the GCC-compatible flags ``-fprofile-generate`` and ``-fprofile-use``. Although these flags are semantically equivalent to their GCC counterparts, they *do not* handle GCC-compatible profiles. They are only meant to implement GCC's semantics with respect to -profile creation and use. +profile creation and use. Flag ``-fcs-profile-generate`` also instruments +programs using the same instrumentation method as ``-fprofile-generate``. .. option:: -fprofile-generate[=<dirname>] @@ -1778,6 +1779,45 @@ profile creation and use. ``LLVM_PROFILE_FILE`` can still be used to override the directory and filename for the profile file at runtime. +.. option:: -fcs-profile-generate[=<dirname>] + + The ``-fcs-profile-generate`` and ``-fcs-profile-generate=`` flags will use + the same instrumentation method, and generate the same profile as in the + ``-fprofile-generate`` and ``-fprofile-generate=`` flags. The difference is + that the instrumentation is performed after inlining so that the resulted + profile has a better context sensitive information. They cannot be used + together with ``-fprofile-generate`` and ``-fprofile-generate=`` flags. + They are typically used in conjunction with ``-fprofile-use`` flag. + The profile generated by ``-fcs-profile-generate`` and ``-fprofile-generate`` + can be merged by llvm-profdata. A use example: + + .. code-block:: console + + $ clang++ -O2 -fprofile-generate=yyy/zzz code.cc -o code + $ ./code + $ llvm-profdata merge -output=code.profdata yyy/zzz/ + + The first few steps are the same as that in ``-fprofile-generate`` + compilation. Then perform a second round of instrumentation. + + .. code-block:: console + + $ clang++ -O2 -fprofile-use=code.profdata -fcs-profile-generate=sss/ttt \ + -o cs_code + $ ./cs_code + $ llvm-profdata merge -output=cs_code.profdata sss/ttt code.profdata + + The resulted ``cs_code.prodata`` combines ``code.profdata`` and the profile + generated from binary ``cs_code``. Profile ``cs_code.profata`` can be used by + ``-fprofile-use`` compilaton. + + .. code-block:: console + + $ clang++ -O2 -fprofile-use=cs_code.profdata + + The above command will read both profiles to the compiler at the identical + point of instrumenations. + .. option:: -fprofile-use[=<pathname>] Without any other arguments, ``-fprofile-use`` behaves identically to |